Conventionally, a magnetic head has been used to write magnetization information in a hard disk drive (HDD). The magnetic head uses a magnetic field generated from a coil. And, the HDD recording density has been required to become higher and higher. As known well, when an HDD magnetic head becomes minute such way to meet the recording domain that becomes minute more and more as a result of achievement of such high density recording, the magnetic field to be generated from the magnetic head becomes weak under the influence of anti-magnetic field components generated from the tip of the magnetic head. In addition, if the recording domain becomes minute such way, the magnetizing direction written in the recording domain becomes thermally unstable and the material of the recording medium comes to be required to become higher in magnetic anisotrophy to overcome the thermally unstable state. Therefore, the HDD recording head also comes to be required to generate a higher writing magnetic field. This is why it has been expected to develop another writing method to be employed for writing magnetization information in such very high density recording operations instead of using the conventional magnetic head. On the other hand, it is also known well that the conventional magnetization information writing method that uses a current causes the power consumption to increase due to the minuteness of the recording domain even in fixed memories represented by the random access memory (MRAM) that employs a non-volatile magnetization method. And, in order to solve such conventional problems, there has been proposed a writing method that makes good use of the spin injection magnetization inverting instead of those magnetization information writing methods that have used a current respectively. The proposed method injects spin-polarized electrons into the subject magnetic material to invert the object magnetization area, thereby writing magnetization information therein. However, because the writing current threshold value is as high as 107A/cm2, the method is also required to be more improved for power consumption.
There is also proposed another writing method, which is a magnetization controlling method that uses an electrical field. For example, the method described in the non-patent document 1 controls the exchange interaction to occur between two ferromagnetic ferromagnetic metal layers by controlling the carrier density in the subject semiconductor layer using an electrical field. The semiconductor layer is structured as a laminated film consisting of a ferromagnetic metal layer, a semiconductor layer, and another ferromagnetic metal layer and the method controls the magnetization state of each of the ferromagnetic metal layers. In another writing method described in the non-patent document 2, the recording medium is provided with an insulating layer in the three-layer structure consisting of a ferromagnetic metal layer, a non-magnetic metal layer, and another ferromagnetic metal layer just like the above laminated layer consisting of a ferromagnetic metal layer, a non-magnetic metal layer, an insulating layer, and another ferromagnetic metal layer, then applies a voltage between the two ferromagnetic metal layers to control the exchange interaction to be generated between those ferromagnetic metal layers, thereby controlling the magnetization state in each of them. On the other hand, the writing method described in the patent document 1 provides a semiconductor layer outside the three-layer laminated film structure consisting of a ferromagnetic metal layer, a non-magnetic metal layer, and a ferromagnetic metal layer to control both width and height of a Schottky barrier to be generated at the phase boundary between each ferromagnetic metal layer and the semiconductor layer with use of an electrical field, thereby controlling the exchange interaction to occur between the ferromagnetic metal layers and cause the state of magnetization to be inverted.
Each of those magnetization information controlling techniques that use an electrical field respectively enables high density recording with low power consumption and they will become favorable techniques in the future. In that connection, there are also other well-known general methods for controlling a position from the surface of a metal probe usually with use of a tunnel current, an optical lever (disclosed in the patent document 2), etc. respectively.
On the other hand, in order to read magnetization information written in a recording medium, an element that employs the GMR (Giant Magneto-Resistance) effect is used. However, because the recording unit is becoming minute more and more due to the requirement of high density recording, such elements are also required to be improved more in sensitivity and reduced in distance from the subject recording medium. And, because the element film of the conventional GMR element cannot be reduced in film thickness, it is difficult for the element to reduce the distance from the recording medium. On the other hand, the element that employs the TMR (Tunneling Magneto-Resistance) effect and is expected to become more sensitive is also doubtful about whether it can stand the GHz level operation, since its resistance itself is large and it employs the tunnel effect. This is why the development of another new reading method has been expected.
The patent document 3 discloses a method for reading magnetization information by detecting a light emission from the recording medium. On the recording medium are disposed a probe electrodes so that they face each other and the applied voltage between the probe and the medium induces the light emission. Those magnetization information techniques that use a metal probe respectively are considered to be favorable as techniques for reproducing nm-order information.
Although it is not a magnetization information detecting technique, it is well known that if a light beam is irradiated on a metal surface while a metal probe is brought closer to the surface, the tunnel current increases there. For example, the non-patent document 3 discloses a phenomenon that if a light beam is irradiated between a metal surface and a metal probe to cause plasmon excitation there, a large direct current flows between them.    [Patent document 1] Official gazette of JP-A No. 196661/2001    [Patent document 2] Official gazette of JP-A No. 73906/1999    [Patent document 3] Official gazette of JP-A No. 250735/1993    [Patent document 4] Official gazette of JP-A No. 215627/2000    [Non-patent document 1] Mattsonet et al, Phys. Rev. Lett. 71, 185(1993)    [Non-patent document 2] Chun-Yoel Youi et al., J. Appl. Phys., 87, 5215(2000)    [Non-patent document 3] Stefan Grafström, Appl. Phys. Rev, 91, 1717(2002).